Cyclic O,O,S-triesters of phosphorodithioic acid

ABSTRACT

Cyclic O,O,S - Triesters of phosphorodithioic acid are excellent accelerators of sulfur vulcanization at elevated temperatures, thereby making possible a considerable reduction in the cure time. Additionally, certain novel compounds of the above class and their preparation are disclosed.

United States Patent Nudenberg et a1. Sept. 2, 1975 [5 CYCLIC 0,0lS-TRIESTERS OF 58 Field of Search 260/927 R PHOSPHORODITHIOIC ACID [75] Inventors: Walter Nudenberg, Newtown, References C d Conn.; Merlin P. Harvey, Denison, UNITED STATES PATENTS Iowa; James Urquhart Mann 3,159,664 12/1964 Bartlett 260/937 Wayne, NJ.

Assignee: Uniroyal, Inc., New York, NY.

Filed: July 17, 1974 Appl. No.: 489,219

Related U.S. Application Data Division of Ser. No. 282,640, Aug. 21, 1972, which is a division of Ser. No. 66,870, Aug. 25, 1970, Pat. No. 3,712,878.

U.S. Cl 260/927 R; 260/923; 260/924; 260/934 Int. Cl. C07d 105/04; CO8f 27/06 Primary Examiner-Anton H. Sutto Attorney, Agent, or FirmRobert J. Patterson [57] ABSTRACT Cyclic 0,0,S Triesters of phosphorodithioic acid are excellent accelerators of sulfur vulcanization at elevated temperatures, thereby making possible a considerable reduction in the cure time. Additionally, certain novel compounds of the above class and their preparation are disclosed.

3 Claims, No Drawings CYCLIC 0,0,S-TRIESTERS OF PHOSPHORODITHTQTQ ACID CROSS-REFERENCES TO RELATED APPLICATIONS This application is adivision of our copending application Ser. No. 282,640, filedAug. 21, 1972 which in turn is a division of our copending application Ser. No. 66,870, filed Aug. 25, 1970, issued on Jan. 23, 1973 as US. Pat. No. 3,7l2,878.

This invention relates to l) the use of 0,0,S- triesters of phosphorodithioic acid to accelerate the sulfur vulcanization of rubbery elastomers at elevated temperatures (i.e., at approximately 400F and higher), (2) vulcanizable compositions containing such triesters, (3) improved cured vulcanizates produced in accordance with the foregoing use and (4) many of the triesters themselves as novel compounds.

The 0,0, S-triesters of phosphorodithioic acid that are within the invention are the addition products, or adducts, resulting from the addition of cyclic 0,0-2,2- dimethyltrimethylene phosphorodithioic acid (hereinafter referred to as DTP for convenience) or homologues across an unsaturated bond, such as, for example,

C=C as in styrene or alkene; C I C- as in phenylacctylcne or acetylene;

H N C as in hcnzalazinc; and

C i N as in acctonitrilc,

The compound to which DTP or its homologues add can have more than one unsaturated bond, and the additive reaction may occur at one or more of such bonds.

The structural formula of DTP is:

Accordingly, the generalized structure of the adduct can be represented follows:

cals) and the alkyl substituted derivatives thereof, and a heterocyclic radical containing one or more heteroatoms selected from sulfur, oxygen and nitrogen. R can also be When R is an aliphatic compound or contains an aliphatic moiety (for instance, when R is an alkyl or an alkyl substituted alicyclic radical), such aliphatic compound or moiety can have from l to 10 carbon atoms, preferably from 1 to 5. Examples of R radicals containing both non-functional and functional moieties follow. Examples of R as a monovalent radical (i.e., x=l are:

Of the 0,0,S-triesters of phosp horodithioic acid.

which fall within the above general formula, many have been previously reported in the literature. J. H. Bartlett (U.S. Pat.No. 3,159,664) discloses, for instance, cyclic 0,0-2,2dimethyltrimethylene S-a-methylbenzyl phosphorodithioate and its method of preparation; and the compound bis(cyclic 0,0-2,2-dimethyltrimethylene) dithiobis( phosphorothioate) has been reported by R. S. Edmundson in Tetrahedron, vol. 21, pp. 2379-2387, (1965). It should be understood, however, that these two compounds have not been previously described as accelerating agents within or without the temperature limits of the invention. Although synergistic combinations of thiazole accelerators and zinc phosphorodithioate 0,0-diesters are known (see U.S. Pat. No. 3,308,103 to Coran), it will be hereinafter shown that such compounds are inferior accelerating agents compared with the compounds of the invention at the elevated curing temperatures of the inventive technique.

A new type of adduct disclosed herein is the result of the addition of DTP and its in molog ues to a C=N- grouping. This is a new reaction previously unreported. This type of adduct is exemplified by cyclic 0,02,2- dimethyltrimethylene S- a-( benzylidenehydrazino) benzyl] phosphorodithioate whose preparation is described in Example 7 below.

PREPARATlON EXAMPLE 1 This example illustrates the preparation of cyclic 0,0-2,Z-dimethyltrimethylene S-a-methylbenzyl phosphorodithioate which is the Markovnikoff 1:1 mole addition product of cyclic 0,0-2,Z-dimethyltrimethylene phosphorodithioic acid and styrene.

10.4 g. (0.1 mole) of peroxide-free styrene was added dropwise during five minutes to a continuously stirred solution of 19.8 g. (0.1 mole) of cyclic (IO-2,2- dimethyltrimethylene phosphorodithioic acid in 200 ml. of reagent benzene at room temperature. The mixture was then stirred and refluxed for nine hours. Evaporation of the solvent gave a liquid which crystallized very slowly.Recrystallization from cyclohexane gave a solid having a melting point of 84 855C. The yield of recrystallized product was 9.5 g. (31.5% of theory).

Analysis for C,,,H,,,O PS Cald. C, 51.64; H, 6.33; P, 10.24; S, 21.21. Found. C, 51.45; H.

The preparation of this particular adduct has been reported in the literature (US. Pat. No. 3,159,664 to .1. H. Bartlett).

EXAMPLE 2 This example illustrates the preparation of the anti- Markovnikoff 1:1 mole addition product of cyclic 0,0,-2,Z-dimethyltrimethylene phosphorodithioic acid and styrene.

A mixture of 20.8 g. (0.2 mole) of commercial grade styrene, 39.6 g. (0.2 mole) of cyclic 0,0-2,2- dimethyltrimethylene phosphorodithioic acid in 100 ml. of reagent benzene and 0.697 g. (0.004 mole) of tertbutyl peroxypivalate (a solution in mineral spirits) was stirred and heated at 45C for 20 minutes and then was heated to reflux. Refluxing and stirring were continued for 7 hours. A 2 ml. portion of the reaction solution was evaporated to dryness and the residue after recrystallization from Skellysolve melted at 67-71C. A second recrystallization from Skellysolve raised the melting point to 7275C. A third recrystallization from Skellysolve raised the melting point to 75.577C. A fourth recrystallization from Skellysolve raised the melting point to 7677.5C. A mixed melting point with cyclic 0,0-2,Z-dimethyltrirnethylene phosphorodithioic acid was 52-59.5C. The mixed melting point with a purified sample (melting point 8485.5C) of the product of Example 1 (the Markovnikoff 1:1 adduct) was 5762C.

Analysis for C l-1, O PS Cald. C, 51.64; H, 6.33; P, 1024; Mol. wt= 302.4. Found. C, 51.63; H, 6.37; P, 10.36; Mol. wt 303.0.

These mixed melting points and the analyses indicate that the product was neither the recovered dithioic acid nor the product from Example 1, but was the anti- Markovnikoff 1:1 mole addition product, viz., cyclic 0,0-2,2dimethyltrimethylene S-phenethyl phos phorodithioate.

EXAMPLE 3 This example illustrates the preparation of cyclic 0,0-2,2-dimethyltrimethylene S-[ l ,2,3u,4,7,7ahexahydro-4,7-methanoinden-2-yl] phosphorodithioate, which is the 1:1 mole adduct of dicyclopentadiene (3a,4,7,7a-tetrahydro-4,7-methanoindene) and cyclic 0,0-2,2-dimethyltrimethylene phosphorodithioic acid (DTP).

39.6 g. (0.2 mole) of cyclic 0,0-2,2- dimethyltrimethylene phosphorodithioic acid was dissolved at room temperature in 200 m1. of dry toluene contained in a 500 ml., 3-neck, round bottom flask equipped with a stirrer, thermometer, reflux condenser and dropping funnel. To the resultant solution, while stirring continuously, was added 25.4 g. (0.2 mole) of clicyclopentadiene through the dropping funnelduring a period of 10 minutes. The ensuing exothermic reaction raised the temperature of the reaction mixture to about 52C. in 10 minutes, the solution remaining colorless. After 24 hours at room temperature, the solution was placed in a beaker on a warm steam bath. As the solvent (toluene) evaporated. a white solid crystallized from solution. After 24 hours, the mixture was filtered to remove the white. solid product which weighed 54.6 g. After recrystallization from Skellysolve and airdrying, the melting point of the product was 1 l31 16C. A second recrystallization from Skellysolve gave a product with a melting point of 113.5115.5C.

Analysis for C H O PS (1:1 mole adduct): Cald. C, 54.52; H, 7.02; P, 9.37; 7( S, 19.41. Found.

C, 53.83; H, 6.82; P, 8.89; S, 18.08.

' An infrared spectrum of the above 1:1 mole adduct showed'the" complete absence ofabsorption at 1610 5 cm, which is characteristic of the double bond between carbon atoms 2 and 3 in the following formula:

mole of m-diiSOpropenyIbenZeneQ' 15.8 g. (0.1 mole) of m-diisopropenylbenzene, which had been purified by passage through chromatographic alumina, was added dropwise while'stirring for six minutes to a solution of 39.6 g. (0.2 mole) of cyclic 0,0-'2,2-dimethyltrimethylene phosphorodithioic acid in 150 ml. of reagent benzene at room temperature. A slightly exothermic reaction caused an elevation of 5C. in the temperature of the reaction mixture. After An absorption maximum was present, however, at 1575 cm, which is characteristic of the double bond between carbon atoms 5 and 6, indicating that the DTP had added across the double bond between carbon atoms 2 and 3.

EXAMPLE 4 dimcthyltrimethylene phosphorodithioic acid.

9.2g. (0.1 mole) norbornadiene was added dropwise during 6-7 minutes to a continuously stirred solution of 39.6 g.

(0.2 mole) cyclic 0,0-2,2- dimcthyltrimethylene phosphorodithioic acid in 150 ml. of reagent benzene at room temperature. An exothermic reaction caused the temperature of the mixture to rise to 585C. When the temperature had dropped to C., product began to crystallize from the reaction mixture. Filtration of the mixture gave 39.0 g. of product (79.9% of theory). The melting point (184-194C.) of the crude product was raised to 1'94'195C. by recrystallization from hot cyclohexane.

Analysis for C, H;,,,O P- ,S 1:2 mole adduct): Cald. "/1 C, 41.79; H, 6.19; P, 12.68; mol. wt., 488.6. Found. C, 41.28; %.H, 5.89; P, 12.74; mol. wt., 459.0.

EXAMPLE 5 thermic reaction did not occur. After heating the reac tion mixture at C. for eight hours, it was placed under reduced pressure (25-35 mm.) at a temperature of 75-85C. on a rotary evaporator for two hours. The residual, viscous liquid weighed 30.3 g. (98% of the- Ory) 3 1 Analysis for C H O PS Cald. 70 C, 50.29; "/1: H, 8.761% P, 9.97; S, 20.66. Found. C, 49.92; 70H, 8.64; P, 9.84; s, 20.0.

stirring for one hour, the mixture was heated to, and maintained at, 6065C., with continuous stirring, for five hours. Evaporation of the solvent left a crystalline product, covered with a thin layer of clear viscous syrup. The melting point of the crude solid, after washing with Skellysolve, was 111.5l15C. Recrystallization from a 4:1 mixture of cyclohexane and benzene gave 24.3 g. of product (43.8% of theory for a 2:1 adduct). Another recrystallization from a 5:1 mixture of Skellysolve and chloroform gave a product melting at 109.5116C.

Analysis for C H O P S (2:1 mole adduct): Cald. C, 47.62; H, 6.54; P, 11.17; S, 23.12; mol. wt., 554.7. Found. C, 47.32; H, 6.32; P, 11.18; S, 25.60; mol. wt., 582.0. 8

EXAMPLE 7 This example illustrates the novel preparation of eyelic 0,0-2,2-dimethyltrimethylene S-[ oz-( benzylidenehydrazino)benzyl] -phosphorodithioate, which is the adduct of one mole of cyclic 0,0-2,2- dimethyltrimethylene phosphorodithioic acid to one mole of l,2-di(benzylidene) hydrazine. 1,2-di(benzylidene )hydrazine itself is the condensation product of 2 moles of benzaldehyde and one. mole of hydrazine.

To a solution of 39.6 g. (0.2 mole) of cyclic 0,0-2,2- dimcthyltrimethylene phosphorodithioic acid in 150 ml. of reagent benzene was added, dropwise, with continuous stirring over a period of 5 minutes at 25C., a solution of 20.8 g. (0.1 mole) of 1,2-di-(benzylidene)- hydrazine. The resultant mild exothermic reaction caused the temperature of the mixture to rise 5C. and within 15 minutes a yellow precipitate began to form. Stirring was discontinued after a total of 2V2 hours, after which the mixture was filtered to isolate the yellow product which had a melting point of 131.5135.5C. Recrystallization of the yellow product from a mixturcof one liter of cyclohexane and 0.5 liter of benzene gave 28.3 g. of product melting at l 32135C. A second recrystallization raised the melting point to 136C.

Analysis for C H N O PS 1:1 mole 7 adduct): Cald. "/1 C, 56.14; "/1. H, 5.70; 7( P, 7.62; 71 S, 15.78. Found. /r C, 54.81; "/1. H, 5.78;' P, 7.77; S, 15.33.

The elemental analysis i'ndicate'd that the product obtained was a 1:1 molar addition product of thephosphorodithioic acid and the azine. 'The yield ofproduct before recrystallization was 37.3 g. or 91.97: of theory.

EXAMPLE 8 This example illustrates thepreparationof cyclic 9 0.0-2,2-dimethyltrimethylene3' S-(oxo)-ahydroxyphenethyl phosphorodithioate. This is the 1:1:1 mole adduct of eyclic' 0,0-2,2- dimethyltrimethylene phosphorodithioic acid, styrene and oxygen. i r

To a solutionof'39.6 g. uzfmoierbf cyclic 0.0-2.2- dimethyltrimethylene phosphorodithioic acid in 125 ml. of reagent benzene in a Parr oxygenator bottle was added 20.8 g. (0.2 mole) of styrene. The, bottle was placed quickly into the oxygenator and forty pounds of oxygen pressure from an oxygen cylinder was applied while shaking the reactants Within 2 hours, a mild exothermic reaction occurred during the uptake of 0.129 moles of oxygen. The reaction mixture was cooled to room temperature. The solid product, weighing only 2.5 grams after drying, was filtered off. The reaction mixture filtrate was diluted with 145 ml. of toluene, washed with 2 100 ml. portions of 8% aqueous sodium bicarbonate solution, 1 100 ml. portion of water, then freed of solvent and dried under reduced pressure (2 mm. at 70C. for two hours). The weight of the very viscous, amber-colored, taffy-like residue was 37 g. (55.3% of theory).

Analysis for C,;,H, O PS Cald. C, 46.69; H,

5.73; "/1 P, 9.26. Found. C, 48.41; H, 5.62;'% P, 9.02.

An infrared spectrum of the chemical,

(C H O PS showed absorption maxima at: (l) 3450 cm (presence of OH group); (2) 685 cm (presence of P=S grouping); (3) 1050 cm and 990 cm (presence of P-O-C grouping).

The reaction of the previous example is not unique. Thus the addition of DTP according to the disclosure in the presence of oxygen under pressure results in the S(oxo)-a-hydroxyform of the resultant compound. For example, in the case of Example 5, 0,022- dimethyltrimethylene S-(oxo)-2-hydroxy-n-octyl phosphorodithioate; and in the case of Example 10, lauryl 3-[cyclic 0,0-2,2-dimethyltrimethylene phosphorodithioyl-( S-oxo)] -2-hydroxypropionate.

EXAMPLE 9 This example illustrates the preparation of his (cyclic Q,O-2,2-dimethyltrimethylene) dithiobis(phosphorothioate).

To a solution of 39.6 g. (0.2 mole) of cyclic 0,0-2,2- dimethyltrimethylene phosphorodithioie acid in 200 ml. of absolute methanol was added a solution of 25.4 g. (0.2 atomic weight) of iodine in 200 ml. of absolute ethanol at 25C. in one portion with continuous stirring. The reaction mixture was stirred continuously for 48 hours, after which a solid product was isolated by filtration. washed with a small amount of absolute ethanol, and then air-dried. Recrystallization from ethanol solution yielded 9.1 gms. (23% of theoryJ-of a white solid with a melting point of l35l 37C.

Analysis for'C H O P S Cald. 7: C, 30.45; 7r H, 5.11:7! P, 15.70. Found. 71 C, 30.77; /1 H, 5.24; 7( P,

15.02. V y t The preparation of this particular product has been reported in the literature (Tetrahedron, vol. 21, pp.

, EXAMPLEIO This example illustrates the preparation of lauryl 2- (cyclic 0,0-2,Z-dimethyltrimethylene phosphorodithioyl) propionate, which is the 1:1 mole adduct of cyclic 0,0-2,2-dimethyltrimethylene phosphorodithioic acid to lauryl acrylate.

To a solution of 19.9 g. (0.1 mole) of cyclic 0,0-2,2- dimethyltrimethylene phosphorodithioic acid in ml. of methylene chloride was added 24 g. (0.1 mole) of lauryl acrylate in small portions over a period of about one-half hour. The reaction mixture was then refluxed for two and one-quarter hours and then washed successively with 50 ml. of saturated, aqueous sodium bicarbonate solution and 100 ml. of distilled water. The washed solution was then treated with Darco (activated charcoal), filtered and evaporated. The residual liquid was placed under reduced pressure (3 mm.) for 5 hours at C. The weight of the clear viscous liquid was 36.2 g. (yield 82.4% of theory, calculated as the 1:1 mole adduct). An infrared spectrum showed the absence of the vinyl unsaturation characteristic of the lauryl acrylate.

Analysis for C H O PS Cald. C, 54.77; 76 H, 8.96; P, 7.06. Found. C, 55.70; H, 8.85; P, 7.07.

The elemental analyses showed that the chemical was the 1:1 mole adduct as indicated above. v

USE OF THE TRlESTERS AS ACCELERATORS In the process of vulcanizing rubbers, it is desirable to accelerate the vulcanization rate so that the production efficiency of a given size vulcanization unit can be increased. One approach to this result has been to raise the vulcanization temperature, but the resulting vulcanizates have shown themselves to be of inferior quality in several respects. The present compounds, on the other hand, are very good co-accelerators of the sulfur vulcanization process at elevated temperatures (i.e., at least about 350 to 400F) when used in combination with such primary accelerators as the thiuram sulfides and disulfides, the dithiocarbamates and the thiazoles. It thus becomes possible to shorten the cure time very substantially. For example a 30 minute cure at 320F. can be shortened to just 5 minutes at 400'F.

EXAMPLE 1 1 This example demonstrates the use of the chemicals of the invention. Normally they function as accelerators and generally can be used with any conventional accelerator, e.g., a thiazole, a dithiocarbamate, a thiuram monosulfide, a thiuram disulfide or a sulfenamide type accelerator.

Code Chemical Name Tetramethylthiuram monosulfide- Zinc 0,0-bis(4methyl-2-pentyl) phosphorodithioate Cyclic 0,0 2,2-dimethyltrimethylcne S-amethylbenzyl phosphorodithioate Cyclic 0,0-2.Z-dimcthyltrimethylene S-[ 1.2. 3:1,4,7,7a hexahydro-4,7-methanoindcne'2- yl] phosphorodithioate E Cyclic 0.0-2,Z-dimethyltrimcthylcne $.S'

(hicyclol 2.2. l ]heptanc2,5-diyl) phosphorodithioate Cyclic 0.0-2,2-dimetl1yltrimethylene S-lmethylheptyl phosphorodithioatc Cyclic 0.0-2,Z-dimethyltrimethylene S,S'- [2 2-( 1,3-phenylene )diisopropyl] phospht'lrodithioatc Cyclic 0,0-2,2-dimcthyltrimethylenc S-lw (hcnzylidenehydrazino )henzyl] phosphoro dithioate l Cyclic 0.0-2,Z-dimethyltrimcthylenc S-(oxo)- u-hydroxyphcncthyl phosphorodithioatc -Continued Code Chemical Name .I Bis( cyclic 0,0-2,2-dimethyltrimethylcne) to K are the nine chemicals whose preparation is given in the above examp les .l, and 3 l in clusive. Two. dif ferent cures, viz. (1) 21. 30 minute cure at 32()F., and (2) a 5 minute cure at,.4.() F.,, were used. Stress-strain dithiobis PMs-Pmmnhiomc) data, including Shore A hardness results, were obtained K g 'yl -(gyallic 3.0-2.2-d rp y y on test pieces which had been vulcanized in a press at as oro l to ro Iona e p p y p p the two differcntatemperatures indicated.

Table 1 Stock 1 2 3 4 5 6 7 8 9 l0 -ll, l2 l3** Base Formulation l83 l83 l83 l83 183 183 I83 183 I83 Hi3 183 I83 lXlS (MBT=().5) Y Chemical K 3.0 Property For 30 Minute Cure at 320F.

Shore A 59 55 47 52 52 47 57 56 52 53 34 47 46 l )Tensile.psi 3210 3350 840 1730 820 940 2800 3230 l 170 2880 Z l040 500 (Z)Elong.,7r 5 l 0 570 I070 900 1000 980 640 640 1000 690 1 l4() 950 l 000 (3 )S-300,psi l 170 N5 .210 325 210 2l5 700 7 10 245 575 90 225 130 Bloom* 2 l l l l l l l l l l Property For 5 Minute Cure at 400F.

Shore A 56 49 52 53 55 51 55 57 55 51 42 Tensile.psi 3220 1870 Z760 2660 2620 2560 2850 2820 3 l 90 2100 l 750 Elongation. 7r 620 790 780 720 750 790 6l0 750 590 5 l0 8l0 5-300, psi 820 405 525 525 455 465 735 805 525 690 260 Bloom" 3 4 l l l l 2 2 2 l l After one l week at room ten'lperature: l none; 2 very slight; 3 moderate; 4 heavy l Tensile strength at break (I) Ultimate elongation (3) Modulus of elasticity at 300'71, elongation Base formulation without 0.5 pt of MBT The compound formula (Base Formulation) used in this evaluation was:

Parts by Weight Royalcne 302* 100.0 HAF black 50.0 Circosol 2XH** 25.0 Zinc oxide Stearic acid 1.0 Sulfur 1.5 2-Mereaptobenzothiazolc 0 5 All ethylene-propylene-dieyclopentadiene terpolymer (EPDM) having an iodine number of H), an ethylenepropylene ratio of 60-40 and a Mooney viscosity (ML-4 at ZIZF.) of 90.

**A naphthenic-type oil; specific gravity 0.9279. Saybolt viscosity at 2l()F. ol seconds. Color ASTM. 2.5. Aniline point. [79F norbornene, I

The results given in Table 1 show that the chemicals of the invention acting as co-accelerators give good high temperature (e.g. 400F.) sulfur cures; substantially equivalent to the cures obtainable with priorart accelerators such as the thiurarn sulfides and the zinc diesters of phosphorodithioic acid. The comparison of the high temperature (400F.) cure with the standard temperature (320F.) cure shows incipient reversion in the Monex stock (A) and appreciable reversion of the zinc diester stock (B). Stocks C to J show that adequate physical properties were developed after only 5 minutes at 400F. with no evidence of reversion. It is obvious that satisfactory cures can be obtained at temperatures between 320F. and 400F. and above by proper adjustment of the cure time. An outstanding characteristic of the chemicals of this invention is that unlike the prior art accelerators they produce vulcanizates with very little or no bloom, thereby making them especially useful in injection molding formulations.

The accelerators of the-invention can .be used to accelerate the sulfur vulcanization of both :low and high unsaturation rubbers. 1

Examples of low unsaturation rubbers are: (l) the EPDM rubbers prepared by interpolymerizing a monomeric mixture containing ethylene, ahigher alpha mono-olefin containing 3l6 carbon atoms and a polyene having two or more carbonto-carbon double bonds. The preferred polyenes include dicyclopentadiene, 1,4-hcxadiene, 1,3-pentadiene, cyclooctadiene, cyclooctatetraene, tridecadiene, 5-methylene-2- 5-ethylidene-2-norborncne,

. 1 3 5-a-propylidene-Z-norbornene, S-isopropylidene-Z- norbornene, 5-n-butylidene-2-norbornene,

5-isobutylidene-2-norbornene, 5-(2-methyl-2- butenyl)-2-norborne ne, 5-(3-methyl-2- butenyl)norbornene and 5-(3,S-dimethylA-hexenyl)- 2-norbornene; (2) the butyl rubbers which are copolymers of about 95 to 99 parts of isobutylene and corre- .spondingly. 5 to '1 parts of isoprene, the solution-polymerization being effected at. low, temperature in the presence of a Friedel-Crafts polymerization catalyst of the type of aluminum chloride or boron trifluoride,

Examples of high unsaturation rubbers include natural rubber, synthetic rubbers, and mixtures thereof. The synthetic rubbers may be the products of the polymerization of various monomers. Such synthetic rubbers are: (1) polymers of butadienes such as 1,3- butadiene, Z-methyll ,3butadiene( isoprene 2- chloro-l ,3-butadiene (chloroprene), 2,3-dimethyll ,3- butadiene piperylene, 1(or 2)-phenyl-l,3-butadiene and copolymers of mixtures thereof; and (2) copolymers of mixtures of one or more of such 1,3-butadienes with up to 70% of such mixtures of one or more monoethylenic monomers which contain a CH =C group. Examples of such monoethylenic monomers include aryl olefms such as styrene, vinylnaphthalene, oz-methylstyrene, p-chlorostyrene, the a-methylenecarboxylic acids and their esters, nitriles, and amides, such as acrylic acid, methyl acrylate, methyl methacrylate, acrylonitrile, methacrylonitrile, methacrylamide; methyl vinyl ether; methyl vinyl ketone; vinylidene chloride; vinylpyridines such as 2-vinylpyridine, 2-methyl-5- vinylpyridine; vinylcarbazole. Commercial synthetic rubbers of this type, made by aqueous emulsion polymerization with a peroxide catalyst, are SBR (copolymer of butadiene and styrene) and NBR (copolymer of butadiene and acrylonitrile). Some of these rubbers may be prepared by the solution polymerization of: 1 1,3-butadienc using as catalyst the reaction product of aluminum trialkyl and titanium tetrachloride or (2) 2- methyl-l,3-butadiene(isoprene), using as catalyst the reaction product of aluminum trialkyl and titanium tetrachloride.

EXAMPLE 12 Results similar to those of example 1 l are obtained when, isoprene (synthetic or natural), styrenebutadiene (SBR) and acrylonitrile-butadiene (NBR) rubbers are used in the inventive techniques.

The inventive accelerators are particularly useful in the production of vulcanized rubber articles reinforced with polyester (linear terephthalate polyester) fibers such as those described by Daniels in US. Pat. No. 3,051,212 and Chantry in US. Pat. No. 3,216,187. These rubber articles include pneumatic tires, V-bclts, flat belts, Timing belts (toothed power or synchronizing belts), footwear, coated fabrics, rubberizedfabric containers, etc. When these articles are made using a rubber vulcanizing system with the so-called delayed action accelerators such as the thiurams or the sulfenamidps, it has been found that these accelerators exert a deleterious effect on the polyester fiber reinforcement. This deleterious effect is accentuated when the article is subjected to elevated temperatures in service, such elevated temperatures arising from environmental heat and/or internal heat generated by repeated flexure as in the case of a pneumatic tire or a belt. Apparently these accelerators during the cure and/or in service form a basic environment which accelerates hydrolytic and/or chain scission of the polyester molecules which in turn causes degradation in the physical properties of the composite article.

The inventive accelerators are uniquely suited as coaccelerators in sulfur vulcanizing systems using thiuram or sulfenamide accelerators because at the elevated curing temperatures of about 400F. they generate acidic products which can counteract the basic products of the thiuram or sulfenamide accelerators. This counteraction by the inventive accelerators results in a less basic environment which in turn greatly reduces the degradation of the polyester fiber reinforcement.

Typical sulfur-containing vulcanizing agents which are examplary of the vulcanizing agents to be used in the inventive technique are:

vulcanizing Agent parts/100 parts rubber Sulfur l.0 2.5

Tuex (tetramethylthiuram 2.0 4.0

disulfide) Ethyl Tuex (tetraethylthiuram 2.5 4.5

disulfide) Vultac (alkyl phenol disulfides) 5.0- 12.0

Sulfasan R (4,4-dithiodimor- 4.0 6.0

pholine) It should be understood that the particular sulfurcontaining vulcanizing agent selected and the amount thereof used for vulcanization is not critical to the practice of the inventive technique; the type and quantity of vulcanizing agent used need only be that as would effect vulcanization under ordinary prior art conditions.

Typical prior art accelerators with which the inventive accelerators can be used are, in addition to MBT and MBTS:

Sodium 2mercaptobenzothiazole Zinc 2-mercaptobenzothiazole 2,2'-dithiobisbenzothiazole 2-(morpholinothio)-benzothiazole 2-benzothiazolyl 1-hexamethyleniminecarbodithioate 2-benzothiazolyl thiolbenzoate l,3-bis( 2-benzothiazolylmercaptomethyl )urea 2-(2,4-dinitrophenylthio)benzothiazole S-( 2-benzothiazolyl N-diethyl dithiocarbamate N-cyclohexylbenzothiazole-2-sulfenamide N-tert-butylbenzothiazole-Z-sulfenamide In general, the weight ratio of the inventive accelerator to the prior art accelerator is from 1:1 to 5: l with about 2:] preferred. The rubber compositions which can be cured with the inventive accelerators can contain the usual added additional ingredients, such as sul fur, pigments, antioxidants and/or antiozonants, fillers. extenders, etc. Curing temperatures can range from about 400F. up to the highest permissible temperature depending upon such well-understood factors as the Having thus described our invention, what we claim 2. A compound having the following formula:

and desire to protect by Letters Patent is: h

1. A compouncl having the following formula: v v i m-phenylenediisopropylene. 10 3. The compound cyclic 0,0-2,2- wherein R and R are C to C,-, alkyl groups; the O pordimethyltrimethylene S,S'- [2,2'-( l ,'3-phenylene) diiso- 'tion represents the optional presence of an oxygen propylene] phosphorodithioate. atom; and R is m-phcnylencdiisopropylene.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. 3,903,205 DATED September 2, 1975 INVENTOR(S) Walter Nudenberg; Merlin P. Harvey; James U. Mann It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 15, line ll: the O por-" should read ---the O por- Signed and Scaled this twentieth Day of April1976 [SEAL] A Itest:

RUTH C. MASON Arresting Officer C. MARSHALL DANN (mnmissimu'r vflarenrs and Trademarks 

1. A COMPOUND OF THE FOLLOWING FORMULA:
 2. A compound having the following formula:
 3. The compound cyclic O,O-2,2-dimethyltrimethylene S,S'' -(2,2''-(1,3-phenylene) diisopropylene) phosphorodithioate. 